1. Field of Invention
Clear water-soluble curcumin complexes with improved light stability and tinctorial power.
2. Background of the Invention
Curcumin, which is the principle yellow pigment in turmeric, is widely used in coloring foods, such as pickles, mustard, and snacks. In some foods such as mustard, ground turmeric is the source of the pigment, and the fibrous cellulosic turmeric root, to which curcumin is not complexed, acts as a bodying agent for the mustard. In pickles, the oleoresin of turmeric is used in a diluted form, in which the curcumin is dissolved and made into an emulsifiable form by the addition of polysorbate 80. In snacks, if the aroma and bitterness of the oleoresin are objectionable, a deflavorized oleoresin may be prepared, and this is used as a polysorbate solution or a microcrystalline suspension in vegetable oil. If only the slight flavor imparted by relatively pure curcumin is tolerable, the curcumin is isolated in crystalline form and either solubilized in polysorbate 80 or used in a microcrystalline form.
At room temperature, curcumin is so insoluble in water or vinegar that virtually no yellow shade is imparted to the liquid. This is why, in aqueous systems, oleoresin turmeric or curcumin dissolved in polysorbate 80, and then emulsified into the aqueous medium, is used. Polysorbate 80 has its drawbacks, however, which include off flavors which are accentuated on aging, and a pro-oxidant effect. It is used because there is no alternative when turmeric colors are desired in aqueous systems. This invention provides an alternative, which overcomes these drawbacks and which, in addition, significantly increases the stability of the colored solution in light.
When used to color fatty foods, microcrystalline forms of the pigment are used. Curcumin has limited solubility in vegetable oil, and will impart a light yellowish cast to it at the saturation point. However, if curcumin crystals are present, these will give a yellower cast but, because of the crystalline structure, they are not efficient as tinctorial agents. In addition, when water is present as in oleomargarine, the curcumin will slowly migrate to sulfite wrapper, which will become stained. This is why margarine sticks, wrapped in paper, are not colored with annattoturmeric mixtures at the present time. This invention provides a turmeric color which will not bleed and stain the sulfite wrapper. Furthermore, since the curcumin is not present in crystalline form, it is efficiently used for its tinctorial power.
If oleoresin turmeric or curcumin is to be used on a snack, it is sometimes dissolved in hot vegetable oil to increase its solubility, and this in turn is sprayed onto the snack. Much of the curcumin will precipitate on cooling of the snack, due to its lower solubility in the oil, and the yellow color is then a combination of dissolved and crystalline curcumin, the latter being an inefficient coloring agent. The present invention surmounts this limitation.
Solutions of curcumin or oleoresin turmeric fade rather rapidly in light. This is why FD&C yellow #5 is widely use to color pickles, in spite of its causing allergic reactions. Likewise, the surface of a margarine or butter containing curcumin and a redder pigment, such as annatto, will change hue in the light as the curcumin fades. Complexing increases light stability, making termination of the use of the objectionable yellow 5 more readily accomplished.